Question

Given a string, add some characters to the from of it so that it becomes a palindrome.
e.g.
1) If input is "abc" then "bcabc" should be returned.
2) input -> "ab" output -> "bab"
3) input -> "a" output -> "a"

Answer 1

#include <stdio.h>                                                                                  
int main()                                                                                          
{                                                                                                   
    char string[500];                                                                               
    int len;                                                                                        
    printf("Enter the input string\n");                                                             
    scanf("%s",string);                                                                             
    len = strlen(string);                                                                           
    char *outputstr = (char *)malloc(len -2);                                                       
    /** We can avoid this extra variable then we need one more integer to point                     
     * the end of the string , so both are same 4 bytes */                                          
    char *substr = ((char *)string) + (len - 1);                                                    
    len = 0;                                                                                        
    /** Instead of while and strcat we can make single loop but that will                           
     * modify the Source string , so made it two loop */                                           
    while(substr != string){                                                                        
                outputstr[len] = *substr;                                                                   
                substr--;                                                                                   
                len++;                                                                                      
    }                                                                                               
    outputstr[len] = '\0';                                                                          
    strcat(outputstr,string);                                                                       
    printf("Out put string %s\n",outputstr);                                                        

}